Results 1 to 13 of 13

Thread: Radiator fan running non-stop, even when car is off, what to do?

  1. #1
    Join Date
    Feb 2015
    Location
    Redondo Beach, CA
    Posts
    179
    My Cars
    00 540i 6MT, 06 911 C2

    Radiator fan running non-stop, even when car is off, what to do?

    Hi

    I have a 2001 330i with about 85k miles. The car was fine yesterday. This morning the battery was totally dead. I assumed that the battery just gave up the ghost without warning and bought a new one (probably a mistake). After putting in the replacement battery the radiator fan came on full blast. Even before the car started. I didn't really notice it at first since I was at the back fooling around with the battery. But after driving it around for a couple of hours it was obvious that there is something wrong with the fan, or a switch or a thermostat or some wiring. The fan is running full speed all the time even when the car is turned off.

    I eventually just unplugged the fan from the electrical system and am trying to figure out what has actually gone wrong so I can replace the appropriate part.

    Any suggestions on how to troubleshoot and locate whatever the offending component is? Now that I think about it, its probably not the thermostat since that is a mechanical piece.

    Hoping to avoid having to bring the car into the shop so they can troubleshoot it.

    Thanks, Derek

  2. #2
    Join Date
    May 2010
    Location
    Honolulu, Hawaii
    Posts
    753
    My Cars
    '73 E9, '94 E34, '02 E46
    IIRC the fan is controlled by a gizmo mounted in the engine bay, not directly by the thermostat/switch. So I'd suspect and investigate the fan controller.

    Another way to do this is to follow the fan power back to ... whatever it takes you to... and verify that item is properly functioning.

    Some use of the Search function, and a report on your findings and results, would be useful. You have to help yourself; although it's okay to ask questions you're expected to be informed of the system you're having issues with. With the depth of knowledge already posted, some research can show you the way and keep the post count down. Resulting in a more satisfied owner.
    Charlie

    Your mission, should you decide to accept it, is to add value to these threads, either by pictures or by descriptions, so the next person with the same or similar problem stands on your shoulders.

  3. #3
    Join Date
    Jul 2011
    Location
    Arlington, VA
    Posts
    9,933
    My Cars
    2018 BMW M240i
    The fan has power at all times. It's controlled by the engine computer (DME in BMWeze). The "box" on top of the fan has nothing to do with the fan. It's called the "AUC" and it samples the air for pollution. There is an electronic box in the fan. This "interprets" the speed commands from the DME into voltages for the fan motor. This results in various fan speeds.

    Read this to get a better understanding of what's happening.
    https://drive.google.com/file/d/0B59...VlE/view?pli=1

  4. #4
    Join Date
    Sep 2012
    Location
    El Paso Del Norte, TX, US
    Posts
    438
    My Cars
    ‘15 F31d Msport
    The fan does not have power with key off.
    There are two relays, one is for the DME, the other is for a/c. They are in the ebox, but I have never had to look for them.
    usually just a relay going bad and sticking closed when they key is off.
    Last edited by Onizukachan; 06-10-2017 at 05:10 AM.
    If I were to give my Touring a first name, I'd probably name it "Alan".
    Mostly because I like puns.
    Mutual Admiration Society #5

  5. #5
    Join Date
    Jul 2011
    Location
    Arlington, VA
    Posts
    9,933
    My Cars
    2018 BMW M240i
    The fan has power at all times. Why? So the DME can command the fan to run if conditions require it to be run.

  6. #6
    Join Date
    Mar 2017
    Location
    Norwich, Connecticut.
    Posts
    486
    My Cars
    E46 wag. E36 convertible
    Quote Originally Posted by MarcoZandrini View Post
    The fan has power at all times. It's controlled by the engine computer (DME in BMWeze). The "box" on top of the fan has nothing to do with the fan. It's called the "AUC" and it samples the air for pollution. There is an electronic box in the fan. This "interprets" the speed commands from the DME into voltages for the fan motor. This results in various fan speeds.

    Read this to get a better understanding of what's happening.
    https://drive.google.com/file/d/0B59...VlE/view?pli=1
    So if you know why his problem is, and you do seem to know what you are talking about...why not just answer his post for a resolve too....it is afterall why we are all here.... instead of leaving his question hanging!
    Last edited by Eaglesail; 06-10-2017 at 03:38 PM.

  7. #7
    Join Date
    Mar 2017
    Location
    Norwich, Connecticut.
    Posts
    486
    My Cars
    E46 wag. E36 convertible
    I cant imagine why there should be any major amp-draw dc component (such as the cooling fan) on any car remaining active after the key ignition is switched off. This could be downright dangerous with a garaged car....or in any event!

  8. #8
    Join Date
    Jul 2011
    Location
    Arlington, VA
    Posts
    9,933
    My Cars
    2018 BMW M240i
    The reason why the efan can be on after the ignition is off is too cool the engine when the driver has shut off the engine after a hot run. The DME uses data from several sensors, including both coolant temperature sensors to determine when the fan needs to run.

    OP, it's likely that your fan's electronics are toast. That's why I gave you the link to BMW-NORTH's document on fan's.

  9. #9
    Join Date
    Feb 2015
    Location
    Redondo Beach, CA
    Posts
    179
    My Cars
    00 540i 6MT, 06 911 C2
    Well I just pulled everything apart and looked at it all very closely.

    The fan is definitely getting power with the ignition off. Based on what I've seen I think this is normal.

    I disassembled the fan as far as I could go without ruining it. It looks like the electronics module is not made to be replaced independently of the fan. In the document that Marco supplied it specifically calls out the failure mode that I'm experiencing. The doc chalks it up to a bad fan control module.

    If there is some way to find a new replacement of the fan control module itself let me know. I'm handy enough with a soldering iron to replace the module. Otherwise I guess I have to get a whole new fan. Which is probably beaucoup bucks.

  10. #10
    Join Date
    Feb 2015
    Location
    Redondo Beach, CA
    Posts
    179
    My Cars
    00 540i 6MT, 06 911 C2
    Looks like the BMW unit is about $500. The other ones are about half that price.

    Does anyone have knowledge of how reliable the aftermarket fans are? The original unit lasted 16 years, which isn't too shabby I guess.

  11. #11
    Join Date
    Jun 2017
    Location
    Suffolk, va
    Posts
    5
    My Cars
    2001 325i
    I have a used but good oem fan.

  12. #12
    Join Date
    Sep 2012
    Location
    El Paso Del Norte, TX, US
    Posts
    438
    My Cars
    ‘15 F31d Msport
    Quote Originally Posted by MarcoZandrini View Post
    The fan has power at all times. Why? So the DME can command the fan to run if conditions require it to be run.
    Between the DME, which is off when the key is off and the fan, there is a relay. So no, the DME can not command the fan to be on except when the key is on because the DME, and the fan both are off with the key off.
    If I were to give my Touring a first name, I'd probably name it "Alan".
    Mostly because I like puns.
    Mutual Admiration Society #5

  13. #13
    Join Date
    Sep 2012
    Location
    El Paso Del Norte, TX, US
    Posts
    438
    My Cars
    ‘15 F31d Msport
    Quote Originally Posted by dealy663 View Post
    Well I just pulled everything apart and looked at it all very closely.

    The fan is definitely getting power with the ignition off. Based on what I've seen I think this is normal.

    I disassembled the fan as far as I could go without ruining it. It looks like the electronics module is not made to be replaced independently of the fan. In the document that Marco supplied it specifically calls out the failure mode that I'm experiencing. The doc chalks it up to a bad fan control module.

    If there is some way to find a new replacement of the fan control module itself let me know. I'm handy enough with a soldering iron to replace the module. Otherwise I guess I have to get a whole new fan. Which is probably beaucoup bucks.
    Crown Vic, Mazda 6?
    If I were to give my Touring a first name, I'd probably name it "Alan".
    Mostly because I like puns.
    Mutual Admiration Society #5

Similar Threads

  1. Auxiliary fan doesn't turn off even when car is off?
    By xomugen in forum 1983 - 1991 (E30)
    Replies: 1
    Last Post: 12-01-2016, 11:16 PM
  2. Car Battery Draining - Light on Dash Blinks even when car is off
    By Jeffersonwillis in forum General BMW Mechanical Help sponsored by RM European Auto Parts
    Replies: 1
    Last Post: 09-04-2016, 10:26 PM
  3. Replies: 12
    Last Post: 01-06-2015, 10:24 AM
  4. Buzzing from radio even when car is off.
    By QuietStorm in forum 1991 - 1999 (E36)
    Replies: 1
    Last Post: 02-10-2011, 03:52 AM
  5. ICV buzzing in 99 M3.....is it normal even when car is off??
    By ultimachi in forum 1992 - 1999 M3 (E36)
    Replies: 0
    Last Post: 04-28-2007, 04:59 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •